The paper discusses the mega-Central Region of Chile or Central Region, as defined by the CIDU/ODEPLAN study. A particular focus is placed on the relationship between the cities of Santiago and Valparaíso. Santiago is acknowledged as an international city connected to global benefit chains, and, at the same time, Valparaíso is found to have growing decline features in terms of its development. To discuss these trends, we first need to develop a conceptual revision of the urban metamorphosis process, starting from the notion of the complete urbanization of society (Lefebvre 1970) and planetary urbanization (Brenner 2013), to then focus particularly on the concepts of global city and mega-region, mainly based on the studies by Sassen (1991; 2007). The question is raised of whether the understanding of the mega-region implies a redistribution of benefits between Santiago and Valparaíso.